The absence of energy transfer between F and M centres in alkali halides: the case of NaF

Abstract

Accurate measurements of the quantum efficiency of the M-centre luminescence in NaF have been performed in the range of 20 - 300 K, by light excitation in the and bands; as in the KCl case, the absence of energy transfer between F and M centres after the F-centre relaxation was ascertained. A discussion of the controversy in the literature concerning the existence of energy transfer is here presented: to reconcile the present results with the data and speculations of different authors it is proposed that the non-radiative energy transfer, if it exists, takes place before or during the F-centre relaxation. The absence of aging effects for the M-centre luminescence in NaF as well as the absence of perturbative effects of magnesium ions in NaF:Mg have been verified.